Perhaps you should try some spelling variations:
"serie lecturas de clacso." » "serie letras de clacso.", "serie lectura de clacso."
"serie cartas la clase." » "serie arte la clase.", "serie notas la clase.", "serie art la clase.", "serie cartas a clase.", "serie carta la clase.", "serie cartas una clase."
"serie actas de clase." » "serie letras de clase.", "serie fichas de clase.", "serie actas del clase.", "serie cartas de clase."

You may be able to get more results by adjusting your search query.

• If you are trying to use Boolean operators, they must be ALL CAPS: (((("serie actas de clase.") OR ("serie cartas la clase."))) OR ("serie lecturas de clacso."))~.
• Removing quotes may allow a broader search: (((( serie actas de clase. ) or ( serie cartas la clase. ))) or ( serie lecturas de clacso. ))~.
• Adding a wildcard symbol may retrieve word variants: (((("serie actas de clase.") or ("serie cartas la clase."))) or ("serie lecturas de clacso."))*.